Camshaft adjusting system having a second camshaft which is supported on the stator in the axial direction

ABSTRACT

A camshaft adjusting system ( 1 ) for a first camshaft ( 2 ) and a second camshaft ( 3 ) which are arranged concentrically with respect to one another is provided, with the second camshaft ( 3 ) being arranged within the first camshaft ( 2 ). A hydraulic camshaft adjuster ( 4 ) of the vane cell type is set up to adjust the first camshaft ( 2 ), and an electric camshaft adjuster ( 5 ) is set up to adjust the second camshaft ( 3 ). The second camshaft ( 3 ) is supported in the axial direction on a stator ( 6 ) of the hydraulic camshaft adjuster ( 4 ). Further, a camshaft adjusting unit is provided including the camshaft adjusting system ( 1 ) and two camshafts ( 2, 3 ).

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. 10 2018 123 178.4, filed Sep. 20, 2018.

TECHNICAL FIELD

A camshaft adjusting system for a first camshaft and a second camshaft which are arranged concentrically with respect to one another, with the second camshaft being arranged within the first camshaft. A hydraulic camshaft adjuster of the vane cell type is set up to adjust the first camshaft, and an electric camshaft adjuster is set up to adjust the second camshaft. Furthermore, a camshaft adjusting unit is provided having the camshaft adjusting system and two camshafts which are arranged concentrically with respect to one another.

BACKGROUND

Camshaft adjusting systems for two camshafts which are arranged concentrically with respect to one another are already known from the prior art. Here, for example, there are differences in the type of the respective adjusters which can be both electric and hydraulic.

Thus, for example, EP 3 141 711 A1 discloses a double camshaft adjuster which is used for an internal combustion engine which has a crankshaft and a valve train which has a first and a second group of cams, it being possible for the phase of the cams in each group to be adapted relative to the phase of the crankshaft independently of the phase of the cams of the other group. The double adjuster has an electric first adjuster for actuating the first group of cams and a hydraulic second adjuster for actuating the second group of cams. The axially coupled construction which is disclosed here between the hydraulic and the electric adjuster is very intensive in terms of installation space, however.

US 2014/0190435 A1 discloses a variable camshaft adjuster with a first fluid transfer arrangement with a fluid transfer sleeve and/or with a multiplicity of pressurized fluid passages, and a fluid transfer plate with a multiplicity of pressurized fluid passages. Each passage extends in order to be connected fluidically to a corresponding circumferentially arranged annular groove segment section for the selective connection to a camshaft adjuster of the vane cell type in a manner which is dependent on an angular orientation of the fluid transfer sleeve during the rotation. Each passage which extends from a corresponding centrally arranged port is connected fluidically to a radially extending passage section and to an arcuately extending passage section.

US 2013/0306011 A1 discloses a variable camshaft adjuster for an internal combustion engine with a concentric camshaft, which camshaft adjuster includes a stator with a rotational axis. An outer rotor can rotate independently relative to the rotational axis of the stator. A combination of an external vane and a cavity can be associated with the external rotor, in order to define first and second external variable volume working chambers. A radially inner rotor can rotate relative to the rotational axis and independently of both the stator and the external rotor. A combination of an external vane and a cavity can be associated with the internal rotor, in order to define first and second internal variable volume working chambers. If the first and second, internal and external chambers are connected selectively to a source for pressurized fluid, the phase orientation of the external and internal rotors relative to one another and in relation to the stator is adjustable.

It is a disadvantage of the previously known systems that the angular adjustment of the first and the second camshaft (also called the intake and exhaust camshafts or the inner and outer shafts) via the adjusting system are dependent on one another. As a result, an increased adjusting range of the inner shaft for counteracting the outer shaft is required. This can firstly be implemented hydraulically only to a limited extent, and secondly the counteraction can prove intensive in terms of time and can be accompanied by a relatively great control fault.

SUMMARY

It is an object to avoid or at least mitigate the disadvantages from the prior art and, in particular, to provide a system which is favorable in terms of costs and installation space and, in particular, solves the disadvantages of the great adjusting range of the inner shaft, the time-intensive counteraction of the inner shaft and the fault-prone control accuracy.

This object is achieved by virtue of the fact that the second camshaft is supported in the axial direction on a stator of the hydraulic camshaft adjuster, via a flex pot and a front cover. Furthermore, the object is also achieved by way of a camshaft adjusting unit having a camshaft adjusting system and two camshafts which are arranged concentrically with respect to one another. Axial fixing of the second adjusting shaft/camshaft is therefore performed.

In the case of said design, the use of a flanged bushing and a separate output internal gear can be dispensed with, as a result of which the overall design can be realized in a particularly flat and less expensive manner.

Advantageous embodiments are described below and in the claims.

For instance, it is advantageous if the front cover which is fastened to the stator of the hydraulic camshaft adjuster and closes the hydraulic camshaft adjuster on a side which faces away from the camshafts has an internal toothing system for supporting the flex pot which is attached to the second camshaft and is equipped to transmit torque from the electric camshaft adjuster.

It is also advantageous here if the front cover is an integral/single-piece/single-material constituent part of the stator or a component which is separate from the latter. If the front cover is an integral constituent part of the stator, connecting elements can also be dispensed with, such as screws. Depending on the installation space, it can also be advantageous, however, if the front cover is configured as a component which is separate from the stator, in order to simplify the assembly, for example.

Furthermore, it is advantageous if the front cover is divided into a stop component and a toothing component which is separate from the latter, or the front cover has both a stop and a toothing section. Here, it is also dependent on the available installation space whether the two functions are integrated into one component and are divided among two separate components, in order to simplify the assembly, for example.

Here, one possible embodiment provides that the stop component or the stop has a shoulder which prevents an axial movement of the flex pot and/or an anti-friction bearing outer shell in the flex pot in the direction of an electric motor of the electric camshaft adjuster, that is to say away from the camshafts. In this way, the stop component ensures that a displacement in the axial direction is limited or prevented.

Furthermore, it has been shown to be advantageous if an adapter part for conducting oil is arranged in the axial direction between the rotor of the hydraulic camshaft adjuster and the flex pot. This adapter part has inner channels and a ring channel on the external diameter, via which the feed and discharge of the control oil into/out of the pressure chambers of the hydraulic adjuster are made possible.

Moreover, it is advantageous if the stop component engages around the front cover. This results in a simple assembly possibility, in a similar manner to a spring cover.

One particularly advantageous embodiment provides here that a frictionally locking connection, for instance a press fit, is configured between the stop component and the front cover.

It is advantageous if the flex pot is connected via an intermediate part to the second camshaft. This makes more precise positioning and/or centering of the flex pot with regard to the camshaft possible.

Furthermore, it has been shown to be advantageous if the electric camshaft adjuster is connected to one of the camshafts by an Oldham coupling/diametrical slot coupling. That is to say, the coupling is configured as a non-switchable, torsionally rigid coupling which can compensate for a radial offset of two parallel shafts. An Oldham coupling is known per se from the prior art, for which reason it is not described in greater detail at this point.

In other words, the adjusting ranges for the outer shaft and for the inner shaft are decoupled by way of the use of an internally toothed front cover of the hydraulic camshaft adjuster as an internal gear for the flex pot which is connected in a torque-proof manner to the inner shaft of the concentric camshaft. The axial mounting of the adjusting shaft takes place either via a stepped portion on the internal diameter of the front cover or via a sheet metal cover which is pressed onto the front cover external diameter, in an analogous manner to the spring cover in the hydraulic adjuster with the spiral spring. An additional adapter is installed between the flex pot and the camshaft, which additional adapter makes the feed and discharge of the control oil into/out of the pressure chambers A and B of the hydraulic adjuster possible by way of its inner channels and the ring channel on the external diameter. A supporting/plain bearing for the flex pot is formed between the adapter external diameter and the rotor internal diameter.

In this way, a particularly flat design of the camshaft adjusting system is possible. A separate output internal gear is dispensed with, as a result of which the system is less expensive and higher pressure intensity of the hydraulic adjuster can be realized in the same radial installation space. The cost ratio of the integration for the hardening of the locking slotted guide and the toothing system in a tempering treatment is improved. Furthermore, the outer shaft and the inner shaft can be adjusted with respect to the crankshaft independently of one another. The electric/hydraulic system therefore makes particularly high adjusting speeds of the inner camshaft possible even at low temperatures below 0° C.

It can therefore also be said that a decoupling of the adjusting ranges for the outer shaft and for the inner shaft is provided by way of the use of an internally toothed front cover of the hydraulic camshaft adjuster as an internal gear for the flex pot which is connected in a torque-proof manner to the inner shaft of the concentric camshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, the embodiments described in greater detail with the aid of figures, in which different embodiments are shown and in which:

FIG. 1 shows a longitudinal sectional view of a camshaft adjusting system according to a first exemplary embodiment in a perspective illustration,

FIG. 2 shows the first exemplary embodiment (shown in FIG. 1) of the camshaft adjusting system in a longitudinal sectional view,

FIG. 3 shows the first exemplary embodiment of the camshaft adjusting system in a perspective view obliquely from the rear,

FIG. 4 shows the first exemplary embodiment of the camshaft adjusting system in a perspective view obliquely from the front,

FIG. 5 shows a cross-sectional view of the camshaft adjusting system in the region of a cover toothing system,

FIG. 6 shows a cross-sectional view of the camshaft adjusting system in the region of a front cover,

FIG. 7 shows a perspective illustration of the front cover in a first exemplary embodiment,

FIG. 8 shows a longitudinal sectional view of the front cover which is shown in FIG. 7,

FIG. 9 shows a longitudinal sectional view of the camshaft adjusting system in a second exemplary embodiment,

FIG. 10 shows a perspective illustration of the front cover in a second exemplary embodiment,

FIG. 11 shows a longitudinal sectional view of the front cover which is shown in FIG. 10, and

FIG. 12 shows a detail view XII from FIG. 11 in an enlarged illustration.

DETAILED DESCRIPTION

The figures are merely diagrammatic in nature and serve only for the comprehension of the embodiments. The same elements are provided with the same designations.

Features of the individual exemplary embodiments can also be realized in other exemplary embodiments. They can therefore be exchanged among one another.

FIGS. 1 to 6 show a camshaft adjusting system 1 in a first exemplary embodiment in different views. FIG. 1 shows the camshaft adjusting system 1 in a longitudinal sectional view. The camshaft adjusting system 1 serves to adjust a first camshaft 2 and a second camshaft 3 which are arranged concentrically with respect to one another, the second camshaft 3 being arranged radially within the first camshaft 2. The first camshaft 2 is adjusted via a hydraulic camshaft adjuster 4 of the vane-cell type, whereas the second camshaft 3 is adjusted via an electric camshaft adjuster 5. This means that the hydraulic camshaft adjuster 4 acts on the outer camshaft 2 in order to adjust a phase position of the latter, and the electric camshaft adjuster 5 acts on the inner camshaft 3 in order to adjust a phase position of the latter.

The hydraulic camshaft adjuster 4 of the vane-cell type has, inter alia, a stator 6 which is closed in the axial direction by way of a ring-like front cover 7 on a side which faces away from the camshafts 2, 3. The front cover 7 has an internal toothing system 8, that is to say a toothing system which is configured on its internal diameter (see also FIGS. 7 and 8) and serves to support a flex pot 9 which is attached to the second camshaft 3 and is equipped to transmit torque from the electric camshaft adjuster 5. To this end, the internal toothing system 8 of the front cover 7 meshes with an external toothing system 10 of the flex pot 9, that is to say with a toothing system which is configured on an external diameter of the flex pot 9. Therefore, the front cover 7 serves as an internal gear for the flex pot 9 and decouples the adjusting ranges for the first camshaft 2 and the second camshaft 3 here.

In the following text, the hydraulic camshaft adjuster 5 will be described in greater detail in relation to FIGS. 1 and 2. As has already been mentioned in the preceding text, the hydraulic camshaft adjuster 4 has a stator 6 and a rotor 11 which is arranged coaxially with respect thereto and lies radially on the inside, the rotor 11 being mounted such that it can be rotated relative to the stator 6. In the exemplary embodiment which is shown here, the stator 6 is configured integrally with a drive gear 12. The drive gear 12, which is configured here as a chain sprocket, is therefore coupled via the adjuster to the camshafts 2, 3 for the introduction of torque.

The electric camshaft adjuster 5 has an electric motor 13 which has an output shaft 14. The latter is coupled in a torque-transmitting manner to the flex pot 9 via an Oldham coupling 15. The flex pot 9 is in turn attached to the inner, that is to say second camshaft 3, via an intermediate part 16 and a central screw 17. The Oldham coupling 15 can compensate for a radial offset of two parallel shafts. The flex pot 9 is mounted via an anti-friction bearing 18 on its internal diameter.

An (additional) adapter part 19 is arranged in the axial direction between the second camshaft 3 and the flex pot 9, which adapter part 19 has inner channels 20 and a ring channel 21 on the external diameter. These serve to feed and discharge the control oil into and out of the pressure chambers A and B of the hydraulic camshaft adjuster 4, which pressure chambers A and B are configured by way of the stator 6 and the rotor 11. A supporting or plain bearing 22 for the flex pot 9 is configured between the external diameter of the adapter part 19 and the internal diameter of the rotor 11.

The hydraulic camshaft adjuster 4 is closed in the axial direction on both sides by in each case one cover, a first cover which is arranged on the left in FIG. 2 (that is to say on the side which faces away from the camshafts 2, 3) corresponding to the front cover 7, and a cover which is arranged on the right in FIG. 2 (that is to say on the side which faces the camshafts 2, 3) being configured as an annular cover 23 with a rotor contact flange 24.

The rotor 11 is mounted on the first camshaft 2 via a bearing point 25. In order to prevent an axial displacement away from the camshafts 2, 3, in particular of the construction which comprises the flex pot 9, a sheet metal cover 26 is provided in the first embodiment, which sheet metal cover 26 serves as a separate stop cover. For this purpose, the sheet metal cover 26 is mounted by a press fit onto the external diameter of the front cover 7.

As can be seen, in particular, in FIGS. 3, 5 and 6, the front cover 7, the hydraulic camshaft adjuster 4 (in this embodiment in the region of the stator 6), and the cover 23 are connected to one another in the axial direction via a plurality of screws 27. As shown here, the screws 7 in this embodiment are arranged distributed uniformly over the circumference (see FIGS. 3, 5 and 6). For this purpose, the corresponding components have openings 28, as shown by way of example on the front cover 7 in FIG. 7.

FIGS. 9 to 12 show the camshaft adjusting system 1 in a second exemplary embodiment. The second embodiment corresponds substantially to the first embodiment, for which reason only the differences will be described in the following text.

In contrast to the first exemplary embodiment which is shown in FIGS. 1 to 8, the second exemplary embodiment does not have a sheet metal cover 26 which serves as a stop component. For this purpose, the front cover 7 has a radially inwardly projecting ring 29 on an axial side (the side which faces away from the camshafts), which ring 29 serves as the stop component in this case (see, in particular, FIGS. 10 to 12). Therefore, both the toothing section 8 which serves as an internal gear for the flex pot 9 and the stop component are integrated into the front cover 7 in the second embodiment.

It can be seen from the detail view in FIG. 12 that the ring 29 is spaced apart from the toothing system 8 via a chamfer, in order not to impair smooth running of the tooth engagement between the internal toothing system 8 of the front cover 7 and the external toothing system 10 of the flex pot 9.

LIST OF DESIGNATIONS

1 Camshaft adjusting system

2 First camshaft

3 Second camshaft

4 Hydraulic camshaft adjuster

5 Electric camshaft adjuster

6 Stator

7 Front cover

8 Internal toothing system

9 Flex pot

10 External toothing system

11 Rotor

12 Drive gear

13 Electric motor

14 Output shaft

15 Oldham coupling

16 Intermediate part

17 Central disk

18 Anti-friction bearing

19 Adapter part

20 Inner channel

21 Ring channel

22 Supporting/plain bearing

23 Cover

24 Rotor contact flange

25 Bearing point

26 Sheet metal cover

27 Screw

28 Opening

29 Ring

30 Chamfer 

1. A camshaft adjusting system for a first camshaft and a second camshaft which are arranged concentrically with respect to one another, the second camshaft being arranged within the first camshaft, the camshaft adjusting system comprising: a hydraulic camshaft adjuster of the vane-cell type configured to adjust the first camshaft, the hydraulic camshaft adjuster including a stator; an electric camshaft adjuster configured to adjust the second camshaft; and the stator including a support that is adapted to axially support the second camshaft.
 2. The camshaft adjusting system as claimed in claim 1, further comprising a front cover fastened to the stator of the hydraulic camshaft adjuster that closes the hydraulic camshaft adjuster on a side which faces away from the camshafts, the front cover including an internal toothing system that supports a flex pot that is adapted to be connected to the second camshaft and is configured to transmit torque from the electric camshaft adjuster.
 3. The camshaft adjusting system as claimed in claim 2, wherein the front cover is an integral constituent part of the stator.
 4. The camshaft adjusting system as claimed in claim 2, wherein the front cover is a component that is separate from the stator.
 5. The camshaft adjusting system as claimed in claim 2, wherein the front cover is divided into a stop component and a toothing component which is separate from the stop component.
 6. The camshaft adjusting system as claimed in claim 5, wherein the stop component has a shoulder which is adapted to prevent an axial movement of at least one of the flex pot or an anti-friction bearing outer shell in the flex pot in a direction of an electric motor of the electric camshaft adjuster.
 7. The camshaft adjusting system as claimed in claim 5, wherein the stop component engages around the front cover.
 8. The camshaft adjusting system as claimed in claim 7, wherein a frictionally locking connection is configured between the stop component and the front cover.
 9. The camshaft adjusting system as claimed in claim 2, wherein the front cover includes both a stop and a toothing section.
 10. The camshaft adjusting system as claimed in claim 9, wherein the stop has a shoulder which is adapted to prevent an axial movement of at least one of the flex pot or an anti-friction bearing outer shell in the flex pot in a direction of an electric motor of the electric camshaft adjuster.
 11. The camshaft adjusting system as claimed in claim 2, further comprising an adapter part configured to conduct oil arranged in an axial direction between a rotor of the hydraulic camshaft adjuster and the flex pot.
 12. The camshaft adjusting system as claimed in claim 2, further comprising an intermediate part by which the flex pot is adapted to be connected to the second camshaft.
 13. A camshaft adjusting unit, comprising: a first camshaft; a second camshaft arranged concentrically within the first camshaft; and a camshaft adjusting system comprising: a hydraulic camshaft adjuster of the vane-cell type connected to the first camshaft, the hydraulic camshaft adjuster including a stator; an electric camshaft adjuster that connected to the second camshaft; and the stator including a support that axially supports the second camshaft.
 14. The camshaft adjusting unit as claimed in claim 13, further comprising a front cover fastened to the stator of the hydraulic camshaft adjuster that closes the hydraulic camshaft adjuster on a side which faces away from the camshafts, the front cover including an internal toothing system that supports a flex pot that is adapted to be connected to the second camshaft and is configured to transmit torque from the electric camshaft adjuster.
 15. The camshaft adjusting unit as claimed in claim 14, wherein the front cover is an integral constituent part of the stator.
 16. The camshaft adjusting unit as claimed in claim 14, wherein the front cover is a component that is separate from the stator.
 17. The camshaft adjusting unit as claimed in claim 14, wherein the front cover is divided into a stop component and a toothing component which is separate from the stop component.
 18. The camshaft adjusting unit as claimed in claim 17, wherein the stop component has a shoulder which is adapted to prevent an axial movement of at least one of the flex pot or an anti-friction bearing outer shell in the flex pot in a direction of an electric motor of the electric camshaft adjuster.
 19. The camshaft adjusting unit as claimed in claim 17, wherein the stop component engages around the front cover.
 20. The camshaft adjusting unit as claimed in claim 19, wherein a frictionally locking connection is configured between the stop component and the front cover. 